Many documents present such pneumatic tyres comprising a self-sealing layer over all or part of their inner surface.
By way of example, document U.S. Pat. No. 4,418,093 presents a process for uniformly positioning a layer of self-sealing material on the inner wall of a vulcanized pneumatic tyre by a combination of rotating the pneumatic tyre followed by oscillating movements until the self-sealing material is sufficiently crosslinked so as to no longer flow.
When the self-sealing layer is positioned in the uncured blank of a pneumatic tyre, one of the problems encountered is due to the very tacky nature of the self-sealing layer which adheres strongly to the curing membrane during the vulcanization phase. After the vulcanized pneumatic tyre is removed from the curing mould, parts of the self-sealing layer may remain adhesively bonded to the wall of the membrane and lead to the rapid scrapping thereof. During this high-temperature vulcanization phase, constituents of the self-sealing layer may also migrate into the curing membrane which may also reduce the service life thereof. The non-stick agents customarily used such as whitewashes or liquid silicones are completely inadequate for solving this problem.
In order to solve this problem, document US 2009/0084482 A1 discloses a pneumatic tyre with a self-sealing layer that is incorporated during the manufacture of the tyre. This pneumatic tyre comprises an outer rubber tread, a carcass reinforcement, a gastight layer positioned on the inside relative to the carcass reinforcement and a protective layer positioned innermost. It also comprises a self-sealing layer adjacent to the separable protective layer and positioned on the inside relative to the gastight layer. The protective layer is a thermoplastic film of nylon or of a mixture of nylon and rubber.
The protective layer facilitates the manufacture of the pneumatic tyre by avoiding any contact between the self-sealing layer and the tools for assembling the blank of the pneumatic tyre. This layer is also said to be separable, that is to say that it can be removed from the surface of the self-sealing layer after the vulcanization of the tyre without taking off all or part of this layer and without tearing.